The ability of a plant to grow and develop under diverse and changing environmental conditions depends on the ability of the plant to utilize carbon and/or nitrogen. Specifically, the accumulation of one or both of these elements suggests that the plant is storing, synthesizing, or utilizing components such as nitrate, amino acids, proteins, sugars and/or carbohydrates to compensate for the changing environment. The balance of carbon and nitrogen in plants is an important aspect of how plants utilize nitrogen efficiently. Carbon skeletons and energy are required in ample supply for nitrogen assimilation and re-assimilation (photorespiratory NH4). Conversely, primary carbon assimilation is highly dependent on nitrogen assimilation because much of the nitrogen in a plant is invested in the proteins and chlorophyll of the photosynthetic machinery. Therefore, fixed carbon must be partitioned between amino acids and carbohydrate synthesis in a flexible manner that is responsive to the external and internal availability of nitrogen. There is a need for compositions and methods that can increase fixed carbon content under varying nitrogen conditions.